Selection system



Aug. 10, 1943. L. A. MEACHAM SELECTION SYSTEM Filed Feb. 1-7, 1942 4 Sheets-Sheet l INVENTOR L.A. MEA CHAM ATTORNEY Aug. 10, 1943. 1.. A. MEACHAM 2,326,478

SELECTION SYSTEM Filed Feb. 17, 1942 4 Sheets-Sheet 2 oEF/cL' FRAAIIE lNl/ENTOR L. A. MEACHAM ATTORMSK 1943. A. MEACHAM SELECTION SYSTEM Filed Feb. 17, 1942 4 Sheets-Sheet 3 ER 23% W53.

HM] N2 lNVENTOR By LAMEACHAM- I A T Tom/EV trunks appear.

secondary switches, and the same is links outgoing from-each of the other eight pri trict secondary switches III,

switch for may be chosen arbitrarily, depending upon the particular conditions existing. It is, however, convenient to assume that there are ten primary switches III'I, Ids, etc., in which the incoming and it will be noted that each trunk appears in ary switches of the district frame Ice, of which there may also be ten, are interconnected with the primary switches by means of link circuits. For example, the ten links I09, I It outgoingfrom the primary switch I01 extend respectively tothe V 1 202 and 203; and in the switch 204 the hold magnets 220, and HI are individual respectively to the ten secondary witches III, H2. Similarly, the

ten links II3, IN extending fromthe priniary I03 appear respectively 'in the ten, true of the switch mary switches. Each oi the IE4, is connected with the ofiice frames by means or junctors outgoing from thedistrict secondary switcheeandincoming to" the office primaryswitches,

If it is "assumed that there are ten district frames, such as the frame I Trunks I30 and IQI appear in switch I01 and trunks I02 and M3 in switch I08,

ofilce frames, "there are correspondingly ten groups or oflice' junct'ors outgoing from the dis trict frame and appearing respectively in the ten" oflice frames.

For example, the ten junctors I I5, IIB', etcl, outgoing from H2, appearrespectivelyin the. ten oifice primary switches 200,

ZIII, etc' ."Inlike manner the other nine groups of junctors including the group II'l,1II8 arejdistributed to the primary switches of the-other nine o'ifice frames, not shown. Like thedistrict irame, the primary and secondary switches of the office frame "208 are interconnected with link circuits. The ten link circuits 202, 20 3 outgoing from primaryoifice switch 202) appear respectively in the ten 'ofiice secondary switches 264; 285; and the ten links 205, 291 outgoing from the primary switch zill appear in the ten secondary switchesv 204 and 2li5." g

The trunks 299, ZIO, 2'II, j2 l2, etc., outgoing from the s'witching stage are distributed among the ten gecondary'officeswitches 204, 205,,jetc;

These trunks may .be divided in any suitable, mannerin groups of varying sizes, For the purp'ose'of illustration it will be assumedthattrunks l 209 and 2 I Iibelong to one group and that trunks 2I0 and 2 I2 belongftoa second group.

- he, crossbar switches are provided with se lect magnets, each of which is individual to. an. incoming circuit and'serves when energized to.

prepare theswitch for subsequently connecting the ten respective dis-' Iprepare two or more idle channels through the I I same switch in the desii-eddirection or directions,

' than one select magnet at a'tirne' The energiza- I the hold magnets I25 and 1'26 are individual respectively to the outgoing junctors I I5 and III;

in'the switch 2% the hold magnets2I8 mam are individual respectively to the outgoing links outgoing trunks 209 and 2H);

In addition, to the select magnets the primary and secondary'switches of the office frame are prcvidedwith spacedischarge tubes, there being one of these tubes ior each select rnagnet. For exampleftubes 222 and 223 are individual to the selectmagnets2 I3 and 2M of the switch 209, and

tubes 22d and 225 ar individual respectively to 1 the select-magnetsflfi and! I'I of the switch 234.

.The purposeof these tubes is'to enable the simultaneous preparation of all switches in the stage so that a connection may subsequently'be completed irom any incoming trunk through an 'idle channel to any desired-outgoing trunk. This l preparation isniade by-en'ergizing ail oi-the se-' lect magnets'representinglinks in the'idle' channels. Since, however, attempts may be made to it is es sential" to prevent the operation of more tion of a single select magnetisaccomplished by the discharge tubes which are soarranged-in a common circuitthat the discharge of one of them creates a blocking voltage which'preventsall others from discharging; Thus the successfully operated tube brings about'the energizationof the associated select magnet to prepare the switch i for that particular channel while theother channels through the same switch remain disabled;

the incoming-circuit to any one of the outgoing circuits. For example, the. primary office switch IO'I .is provided with select magnets I I9 and I20 which are individual respectively to the incornfingtrunks I00 and IOI and serve to prepare the 1 extending these trunks over any of the outgoing links I09 and I III. 'The ofiice secondary switch I II is provided with select magnets IZI,

;I2'2 which are. individual respectively toth'e-incoming links I09 and II3; the oiiice primary switch 290 is providedwith selectmag'nets 213,

ondary oiiice switches,

2 which are individual to the incoming junc tors I I5 and ZIBjIand'the omce secondary switch 204 is provided with select magnets ZISand 2I'I' which are individual re'spectively to the incoming links 262 andZIli. The switches are also provided with' holdmagnets, oneifor each oi the outgoing circuits. fi vhen one of these hold magnets i operated following the previous energization 'The testing and switchpreparing' operation is initiated by 'applying -an e1ectrical conditionto the calling incoming trunk appearing in a par- 'ticular oneof the districtprirnary switches. This" conditionca'uses a test potential to be projected" simultaneously overall links outgoing from the said p'articularoriginating switch to all of the ten secondary district switches in which these links appear,'cau sing the operation of the cor- V responding switches. {Ih'e operatio'n'of the secondary select select magnets of the secondary magnets causes the test potential'to be further projected over all idle junctors outgoing from such secondary switches to' the corresponding primary oflice switchescausing the operation of the as; sociatedselect tubesand'magn'ets. The operation of the prirn'ary office select magnets causes the further extension of the-test potential over all extending to the corresponding sec- 1 The test potential apidle links plied to these idle links causes ionize their control or startinggaps, However, thesesecondary oflics'elect tubes do not operate sufiiciently to cause the energization of the corf Thu Lall channels responding select magnets; in the whole switching stage which extend from v v the corresponding select tubes at'the secondary oiliceswitches tol itsiclo'sedv contacts, switch .arm 330::(position conductor 33I,-winding,of. relay I28 to battery. i Relay I28 relates to the office frame208 in whichv the desired trunk igroupappears 'and serves to complete: control. circuits for the links extending 'from'the district-framel04 to the oilice frame-.208; Thisrelayis selected'underthelcontrol of the register 300 which has .been positioned in accordance with one of the code digitsrfilf desirable the .selectionmay, of .course, be placed under the control. of: two of thebode digitxregistersk: In a similar manner relay I50'relates to another frame of oificeswitches and. serves to perform a corresponding 'function with respect tonthe'. links. outgoing. from the district frame I04 to such other oificeframe...

.Relay 320-;in. operating closes .a" circuit .-.from ground through its contacts, throughconductor 332, connectorx305; conductor'333,-conductor I30;

' windingof select magnet I.I9-tobatterygiMagnetselect, magnet I.2I-. of the'secondary switch III.. Magnet vI 2 I 'operatesand .prepares the switch I H for connecting. the incoming link I09 :to any idle.

oneof the ten-outgoingjunctorsl I5, I I1.-. Likewise, if link IIO outgoing from switch I01.is idle,

the grounded conductor I3I is extended through the normal contactsof magnet I24, conductor I33, .throughthewinding of. select magnet I34 c to ;battery.. In a similar. manner circuits are closed corresponding to all "other, idle links. outhichiisthe only' going from the primary. switch I01;

Assuming that :junctor I I5, junctor outgoing; from the switch III to the desired oiiice frame 208, is-s'idle, a test'circuitis closed;.frombattery through the contacts? of operated magnet I2I', resistor. I35, conductor I35, normal contacts of magnet I25, conductor I31, closed contacts of; relay I28, conductor 232 t0 the starting'anode:.233 of'select tube 222.

---Likew ise if junctor H5 is idle, a .test circuit is' closedu fromgbattery through .the. contacts of I magnet, I34, resisto I30, contacts of hold magnet I39, conductor I5I, closed contacts of relay I2B,-,conductor. 234 .to the starting anode 236 of the select tube 235.. 'Since the negative pole of battery is connected through the inductance 231 tothestartingcathode 2300f tube 222,'the tube ionizes its starting gap; anda circuit is closed as. follows through the main discharge gap lof the tube: positive pole of battery I40,

closed. contacts of relay I28, conductor I29, conductor 239, main anode 240, ma'incathode 24l',

winding of select magnet: 2I3. to the negative pole of battery. In like manner the tube1235.

discharges and a circuit is; closed from battery I40 'over conductor-I20,-v conductor 242, main anode and main cathode of. tube .235, winding of selectmagnet 243 to the negative pole of'battery, And in a similar manner the select tubes of otherofilce primary switches ofthe frame 208 are dischargedprovided there are I corresponding idle-l nks extending fromthe primaryswitch I01 and. thence from district switches. It will be noted that the inductance-231 is common to the starting cathodes of; all tubes inthe switch 200.- As soon as the the corresponding l secondary lay 328' closes a circuit :ir'om ground through startingjg'ap of .one. of these tubes ionizesga" potential is produced by. the inductance. 231

which lowers'thevoltage across all othertubesfl to prevent a sec'ondone from energizing its start-I ing gap incase a, test .should be made. at this time from someother district frame. Also there is sufiicient resistance inthe inductance coil1231. tomaintain the. lockout voltage after. the initial transient. is dissipated.v Thus only one ofthe select" tubes in. each. of the office primary.

switches200; 20I can energize at a time..

.Ifat'this time the link 202 outgoing from the switc'h..200 'to theswitch 204 is idle, a test circuit-isclosed from the positive pole of battery. throughthe contacts of select magnet-2l3, re- 1 sistor. 244,'norrnal.contacts of bold magnet 2I8,

conductor 245 to the starting anode of: the tube 224. Similarly ifizthe link203' is idle the negative pole.. of. battery ;is extended throughresistor 244, normal contacts of hold magnet 2I0,-

conductor 241 to the starting anode of select. tube 214. Likewise, if'the links 205 and 201 outgoing from the switch..20I are idle, circuits are closed from the negative pole of battery through:

the contacts of select magnet.243,t common -.re'-- sistor 240, thence through the normal contacts ofyholdmagnets 249 and 250and-over the cor-. f responding conductors to the control anodesof theselect tubesj225 and 215. Thus all four of .the tubes illustrated, tubes224, 225,;214 and 215, have starting potential applied to their starting anodes. And, of course, all other select tubes are similarly prepared which correspond...

to idlechannels extending to. thepremaining secondaryofiice switches. :Since the-negative 'I pole of battery is. connected through the common ii resistance 245 to the starting cathodes of Iall tubes inthe switch 204, the first one of these tubes to ionize its control gap sets up a potential across the resistance 245 which lowers. the voltage of the control gaps of the remaining tubes to prevent another one of them from'ionizing.-

And the same is true of the remaining secondary office switches. Thus only one select tubesucceeds in ionizing its control gap in-each-of these secondary switches. It will be assumed that the tube 224' of switch 204 andthe tube 214-of'the switch 205 are the ones that ionize their control I gaps. a s 1 When tube 224 ionize's its control gap, a circuit is established from the positive pole of bat-- tery I46, contact of relay I28 conductor -25I, through the winding of relay 252, conductor 253,

main anode of tube 224, main'cathode through-* the'winding'of select magnet 2H3 to the negative pole of battery; "Relay 252 operates in this circuit, but its-resistance is too high to. permit Sui-- ficientcui'rent to how tocperate the select mag-- net j2l5l Assumingat this time that-wthe trunk 209 of the desired group is idle, a circuit is closed from'thenegative pole of battery ithrough'the common inductance 254, conductor 250, contacts of'relay 252, normal contacts of select magnet 220, conductor 255' to the starting cathode 256 of tube 225[ Also intheswitch 205 the'ioni'za tion of the control. gap of tube 214 prepares: a circuit from the positive pole of battery I46;"conductor 251;through' the winding of relay-"2581 thence through the mairi gap of the tube' 214f and the winding of select magnet 259 to the nega also idle, a circuit is closed-through-the common inductance 254, conductor 250, contacts of relay If at ductor 252 to the starting cathode 2-53 of. tube 228. Thus .a, negative potentialis applied through the commoninductancezfl tothe starting cathodes of all tubes corresponding to idle trunks'2il9, 5 '2I Iofthe desiredgroup. vIt will also be noted that negative potential is applied through the common inductor. ZEAand "through the normal whack .contactsvof the hold magnets to the starting cathodes of thetubesiof all idletrunks of all other groups appearing inswitches which have their corresponding relays 252, Efifioperated. In other words, the test which has been made through the district and ofiice frames of; the

switching stage as above explainei prepares the 1-5 idle channels through .theseframes for connectionto the idle trunks of lallgroups, outgoing from the secondary oflice switches. f However, since only one group is desired-namelythegroup containing the trunksZlBQ and 2H, the-selection isconfined to a trunkin this group under. control of the sender-marker in afmanner which willnow :be explained; I

Returning now to the .point in the description-where theoscillator 3046s tuned by the digitsregistered on -registers 3M and -3 92,-it may be assumed that the .irequency thusproducedby the oscillator is the one :tO WhiCh the circuit All: is tuned. Therefore the discharge tube 4%. will i v I --operate to the exclusion of' the corresponding v hold magnet'I'23 to battery. Magnet I2 3 operatesv switch Iii! toconnectthe calling incoming trunk "160 to the link Hi9. Thus thecallingtrunk lilll "is extended through the links of the district and winbes'oi all'other tuned circuits in the group. The

circuit between the oscillator and the tunedcir- .cuit 4B2 maybe traced from conductor 3 I2, brush 32s; conductor 3m through the wnnecmr' sca,

conductor 122B, capacitance 4B8, inductancedml, 35" conductor M], connector 393,.conductorfilfi, brush 32] to conductorSIB.

Since the input circuit of the tube 4% istuned to this particular frequency, a voltage rof suincient magnitude to ionize the control-gap of the tube isaapplied' through the resistor-Hit to the -.starting anode MZ'and to the starting cathode llii. The starting gap ionizes, the main gap of the tube discharges, and current flows .from the positive .pole

of battery M 1, alternating current generator 445,:

winding of relay 401, main anode 4 I5, main cath- [ode M1 to ground. The relay All? operates and app ies the positive pole of battery llscver conductor 419 to the starting anode 239 of tube to the. starting anode 2% of the. tube 228 so of the select tubes of the office secondary switches, .and similarly to the starting anodes of all; tubes individual to other, trunks in this group Since as "above described negative potential has aready been applied to the -starting cathodes of these tubes, one of them will commence 'tthegy55 ionization'of its control gap. As soon as this I occurs-a voltagel is developed across the common inductance 'zfi lavhich lowers the voltage across the gaps of all other tubes to prevent another one from completing its ionization. As-

hun ng that the wheeze is one that successfully ionizes its control gap, eiiecting the selection: of M the trunk 25$ for use, -a circuit is completed from battery I46, conductor 25L winding of relay 2%,

in this circuit, hut its resistance is too high to hermit the'operation of the hold magnet 22!).

when relay 254 operates it 01056812; circuit in shunt of relay 252 traceable from battery on conductor i251, contacts of relay 2554, resistor 25'! w thence through theetube :-224:'and-select magnet 21%. The magnet'2l6 operates. in this 'circuitand prepares the switch 26. 1: forwoperation. Magnet .75

r e,32c,47 s I i v 7 Q 7 v .258, normal contacts-of select magnet 26I,.con- Y .Zlticloses a low resistance path iromtheposh --tive pole of battery 2% through the contacts of magnet 2H6; resistor 269., conductor ,255 and thence astraced; through the tube 226 and hold magnet 22d. Magnet 223- operates in this fcircuit and completesthe operation of the switch to connect'link 252 to the selected idie outgoing trunk r .209. "It will be noted. thatjcurrent in the com-V mon resistor 26'! develops a lockout voltage to prevent'the operation of a second one of the select tubesof switch Zilllin the event that the starting gap ofa-second' tube should ionize following the operation of. the chosen tube 224.

Likewise the common resistor 259 developsla lockout voltage after tube 226 operates toprevent the operation of. another itube associated 'with the trunks. outgoing from switch 204,

When magnet 2I'6 operatesit closes a circuit from ground through its contacts,- conductOr Z'lU through-the winding of hold magnet '2 iii. Magnet 2 IS operates the switch 2% to connect the junctor Hlito the link2ll2. The grounded conductor 279 is now-extended through the contacts of the switch: thence iover conductor 2H through the Winding of holdmagnet I25 to battery. fl\/Iagnet I25 operates the switch ii I to connect thejunctor I0 to thelink 'I Ill. The grounded conductor 2' is thus eXtendedthrough-the contacts of switch lII over-conductor It] through the winding of (juice switches to the] selected idIeoutgoing trunk 2219. In the well-knownmanner acontrol ground the connection through the switching stage the circuit of relay I28 is opened in the sendermarkeriandthis relay releases, The release of relay I28 quenches allo-f the operated Select tubes of the primary oiiice switches, including tubes222 and 235. The quenching of these tubes permits 1 the release" of the associated magnets zlii, 243, etc; The'releaseof-the select magnets removes the operating pctential from the starting anodes The release of relay also causes'the release of relays 252 and 25d and magnet 2H; and quenches tube 224; I

tube 226, thus restoring the control relays, mag-- Therele'ase of magnet 216 quenches nets and tubes of switch 294, while the establishedconnection is held by thehold magnet 220.

Also at the proper timerelay 329 in the sendere marker releases and opens the energizing circuit of the select magnet H9. The release of these- 0 lect magnet IIS removes ground potential from conductor I 3! permitting the release" of'all operated select magnets of'the secondary district switches, such as magnets I2 L134, etc.

The connection" having "been established through the selective switching stage, the sendermarker 3% can now be released in any'wellknown mannerh Upon release of the sender- "marker the registers Sill), 3M and 302 and the steering switch 358 are restored. to their normal positions;

7 Fig. 5-shows a modification of the reactarice elements selectable by the registers 3E and 3B2 for tuning oscillatortil l. In this'figure reactance units selected by both the tens and units resis- 'ters comprise "both inductance and' capacitance potential is applied to the conductor 142' of the trunk I to hold the magnets I23, I25, 2'I8,and

.For example, the tens register switch selects The advantage of using parallel inductances' and condensers in each unit ,is an improvement in the range of the antiresonant impedance of the combined elements introduced into the oscillator circuit.

Fig. 6 shows an alternative arrangement of the tunable selecting mechanism in the sendermarker. In this figure the marker is provided with two oscillators 6G0 and 60!, each of which is capable of beingtuned to produce a plurality of distinct frequencies. One or more than one of the code digits transmitted to the sendermarker serve to tune the oscillator 600 to produce inits output circuit 602 a distinctive frequency, corresponding to the digit. This frequency is selected by the corresponding. one of the tuned circuits 603, 694, etc., to efiect the selection of the desired one of a number of groups 605, 606 of tuned circuits. The succeeeding digits serve to tune the second oscillator GM to produce in its output circuit 601 a particular frequency for selecting one of the plurality of individual tuned circuits 608, 609, 6") of the selected group. Thus the first two digits of the code may serve to select one of the groups 605, 606, and the last two digits of the code may ser e to. select one of the individual circuits E08, 659, 5H1 of the selected group. The oscillators 6M and 60! maybe tunable to produce the same or difierent distinctive frequencies. l V

The dischar e tubes disclosed herein may be of any well-known type such as those having gasfilled envelopes and cold cathodes. A tube of the tvre having a separate con rol or-starting gap formed bv a start ng anode and a starting cathode is disclosed in the patent to Holden No. 2.273958 of Feb. 24. 1942. Y

What is claimed is: 1. The combination in a telephonesystem oi a switching stage comprising a plurality of auto mat c switches, a plurality of trunks appearing in' said switches, sa d t unks having d fferent designations. means for receiving and registering the diii'erent designations corresponding to said trunks. a generator for generating voltage of a plurality of 'diflerent frequencies, a plurality of tuned circuits'connectable to aid generator, each of said circuits being tuned to and responsiveto voltage of a diilerent'one of said frequencies. means dependent on the designation registered by said registering means for causing said generator to generate voltage of a corresponding one of sa d frequencies and to apply said volta e to said tuned ci cu ts. controlled by the tuned circuit which responds to the generated voltage for selectin the corresponding one of said trunks for use. and means for operating saidswitches to establish a connection over the selected trunk.

' 2. The comb nat on'in a telephone system of a switchin stage comprising a plurality'of auto-- matic switches, a lurali y of trunks appear ng in saidswitches, said trunks having different desi nations, means for receiving and registering the different designations corresponding to said trunks, an oscillation generator for generating voltage of aplurality of, different. frequencies,

means dependento-n'the designations registered for Varying the tuning 'of said oscillator to generate voltages of a corresponding one of said erated voltage for selecting the corresponding one of said trunks for use, and means for operating said switches to establish a connection over the selected trunks. I L

3. The combination in a telephone system of a switching stage comprising a plurality of automatic'switches, a plurality of trunks appearing in said switches, said trunks having difierent designations, means for sendingimpulses corresponding to said designations, registers responsive to aid impulses for registering the designations of said trunks, an oscillation generator for generating voltage of a plurality of difierent frequencies, tuning means selectable by saidregisters for tuning said oscillator v to produce voltage of a corresponding frequency, a plurality of tunedcircuits each tuned to and responsive to a different one of said frequencies, means for connecting said oscillator to said tuned circuits, means controlled by the tuned circuit which responds to the generated voltage for selecting thecorresponding one of said trunks for use, and means for operating said switches to establish a connection over the selected trunks.

4..The combination in a telephone system of a switching stage comprising a plurality of automatic switches, a plurality of trunks appearing in said switches, said trunks having different designations, means for sending impulses correspondingto saiddesignations, registers responsive to said impulses for registering the designations of said trunks, an oscillation generator Iorgenerating voltage of a plurality of diflerent frequencies, inductances and capacitances' of different values, said registers servingto select different combinations of said inductances and capacitances to tune said oscillator to produce avoltage ofthe corresponding frequency, a plurality of tuned circuits, each tuned to and responsive to a different one of said frequencies, means 'for connecting said'oscillator to said tuned circuits,

means controlled bythe tuned circuitwhich responds to-the generated voltage for selecting the corresponding one of said trunks for use, and means for operating said switches to establish a connection over the selected trunks. v

a 5. The combination in a telephone system of a switching stage comprising a plurality or automatic switches, a plurality of groups of trunks appearing in said switches, said trunk groups having different designations, means for transmitting impulses corresponding to the difierent trunk group designations, means for receiving. and registering said impulses, a generator for generating voltage of a plurality of difierent frequencies, a plurality of tuned circuits connectable to said generator, each of said circuits being tuned to a voltage of a'diflerent one of said frequencies, means dependent on the designation registered for causing said generator to produce voltage 01 the corresponding frequency and to apply said voltage to said tuned circuits, means controlled by the tuned circuit which operates in response to the said voltage for selecting the corresponding one of said trunk groups, and means for operating said switches to establish a connection over i an, idle trunk of the selected group.

6. The combination in a telephone system of a switching stage comprising a plurality of automatic switches, a plurality of groups of trunks appearing in said switches, said trunk groups having difi'erent designations, means for transmitting impulses correspondingto the different" trunk group designations, a selecting and con trolling mechanism common to said trunk groups, said mechanism including registers and an oscillation generator, said registers'responding to said impulses forregistering the designations of said trunk groups, means controlled by said registers for tuning said oscillator to produce a plurality circuits connectable tosaid'oscillation generator, said circuits being tuned respectively to saidfrequencies, means controlled by the tuned circuit which responds to the generated Voltageforsbr- LARNED A, MEACHAM,

, V 'j' r of difierent frequencies'which correspond respec-f 1 I tively to said trunk groups, apluralityflof tuned 

